Shore Line Erosion Control

ABSTRACT

A novel design for eliminating bank and cliff erosion on sandy beaches and having a very small width footprint on the beach is provided by an adjustable metal frame main structure with curved corrugated steel sheets coated with a special sandy colored polyurethane attached to the frame so as to curve upwardly to a generally vertical upper edge. A base sheet of the frame is held down against the sand by heavy rock so that the toe of the curved sheet is buried three feet below the sand surface. The design does not require any armor rock in front of the curved sheet.

This application claim the benefit under 35 USC 119(e) of Provisional Application 61/492,016 filed Jun. 1, 2011.

This invention relates to an apparatus for control of erosion at the shore line of a body of water.

BACKGROUND OF THE INVENTION

There has been some severe erosion taking place on lake shores in sandy beach areas in Canada and the United States and this has become a wide scale problem.

One of the problems with traditional erosion protection designs using conventional revetments is the large width of space required to complete a design on sandy beaches. If the shoreline of the beach area where the erosion is taking place is populated with cottages and is used as recreational space for swimming and sun bathing there is a conflict for beach usage. Sun bathers want more beach during the summer and cottage owners see their frontage being eroded away. For traditional revetments to function requires the placement of armor rock in front of the cliff or eroding area in order to dissipate the kinetic energy of the waves as they move towards the bank or cliff zone. In some cases up to forty or fifty feet of sandy beach may be required for the placement of this rock. In many cases this is not an acceptable use of the beach.

SUMMARY OF THE INVENTION

According to the invention there is provided an apparatus for control of erosion at the shore line of a body of water at or near an edge of the surface of the body of water comprising:

-   -   a frame for mounting at the shore line with a base for engaging         into the ground and an adjustable upper portion for extending         upwardly from the ground;     -   at least one curved sheet mounted on and located by the frame;     -   the curved sheet having a lower edge arranged relative to the         frame so as to be located at a position below the ground         surface;     -   the curved sheet or sheets having an upper edge arranged         relative to the frame so as to be located at a position above         the water or beach surface;

the curved sheet or sheets having a concave front surface extending from the bottom edge upwardly to the upper surface and curved so that an angle of the surface to horizontal planes increases from the horizontal planes adjacent to the bottom edge to horizontal planes adjacent to the upper edge.

The height of the upper edge of the curved sheet is located at a position above the water surface which is sufficient to reach the level of the adjacent cliff level so that this can vary depending upon the height of the cliff. In some cases where the required height is less than the typical sheet height of 9.6 feet, a single sheet can be used. In some cases the sheet is connected to a second curved sheet if the eroded shoreline is at a height higher than one curved sheet.

Preferably the curved sheet is substantially vertical at the upper edge.

Preferably the frame is a bolt together structure formed of a plurality of horizontal rails supporting the curved sheet including a bottom rail at or adjacent to the bottom edge and a top rail at or adjacent to the top edge and the rails are connected to upstanding supports which extend from the rails downwardly to the base. The height of the frame is preferably adjustable to accommodate different heights of cliff and the required height of the sheets. This can be done by bolting together additional pieces or by adjustable coupling of one frame member to another.

Preferably the base includes a receptacle in the form of a heavier gauge corrugated galvanized flat base sheet for receiving ballast such as rocks to hold down the frame in the ground. That is, the base is held down against the sand by heavy rock such that any lateral forces pushing from the cliff side are counterbalanced by this rock by at least a factor of two.

Preferably there is provided a plurality of curved panels arranged side by side with the curved sheet panels being corrugated with channels which extend longitudinally from the bottom edge to the top edge. Such panels are readily available from grain bins or similar constructions with the corrugations providing sufficient stiffness to maintain the curvatures of the panels.

Preferably the curved panels are coated with a sand colored coating at least on the concave front surface.

After installation the void behind the curved sheet is filled with a drainage material. No armor rock is required in front of the curved sheet to provide a very short width profile on the beach.

A hand railing can be attached to the frame at or adjacent to the upper edge to provide a safe walkway behind the revetment along the splash apron.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of revetment design showing curve S1 and the splash apron.

FIG. 2 is an isometric view of the assembled apparatus separated from the installation showing the components.

DETAILED DESCRIPTION

The apparatus for control of erosion at the shore line of a body of water at an edge of the surface of the body of water includes a frame 10 for mounting at the shore line with a base 20 for engaging into the ground and an adjustable upper portion 12 for extending upwardly from the ground. On the frame is mounted a row of panels 13 mounted side by side on and located by the frame. The panels form a curved sheet 14 of the top part of the structure which has a lower edge 15 and an upper edge 16. The sheet can be formed of a single panel 14 or can include a second panel 14A connected at the bottom edge 14B of the upper panel as required. The lower edge 15 is located at a position below the ground surface at a bottom and forwardmost point forming a toe 15A. The curved sheet 14 together with the lower sheet 14A has a concave front surface 140 extending from the bottom edge 15 below the ground surface continuing upwardly to the upper surface 16 and curved so that an angle of the surface to horizontal planes increases from the horizontal planes adjacent the bottom edge to horizontal planes adjacent to the upper edge where the curved sheet is substantially vertical.

The frame is a bolt together adjustable structure formed of a plurality of horizontal rails 17 supporting the curved sheet or sheets including a bottom rail 17C at or adjacent to the bottom edge of the bottom and a middle rail 17B at or adjacent to the bottom edge 15 and a top rail 17A at or adjacent to the top edge 16 and the rails are connected to upstanding adjustable supports 18 including the rear longest posts 18A, middle posts 18B and the short front posts 18C which extend from the rails downwardly to the base. The top sheet 14 is also supported by curved beams 19 which follow the curvature behind the sheet and extend downwardly and forwardly to the lowermost rail 17C at the top of the posts 18C.

The base attached at the bottom of the posts 18 includes a receptacle in the form of a galvanized flat base sheet 20 also formed from corrugated panels for receiving ballast such as rocks to hold down the frame in the ground. The base sheet 20 is carried on a plurality of beams 22 connected to the bottom of the posts 18A, 18B and 18C so that the frame forms a rigid structure attached to the base sheet 20 and carrying the sheet 14 and the lower sheet at its elevated position above the base sheet.

The active part of the curved sheet 14 is that from just above ground or beach level to the top edge 16. The curved panels are coated with a sand colored coating on the concave front surface.

After installation the void V behind the curved sheets is filled with a drainage material. No armor rock is required in front of the curved sheet to provide a very short width profile on the beach. A railing 21 can be attached to the frame at the top rail 17A to provide a safe walkway behind the revetment.

The Southern basin of Lake Winnipeg similar to other North American lakes is a prime candidate for this new design. The first observation that should be made is that the footprint of this design will take up considerably less sandy beach than a traditional design as there is no need to provide armor rock in front of this configuration. The design is comprised of a galvanized curved sheet of corrugated steel such that a line tangent at the top edge of the curved steel sheet is almost vertical. A second observation is the flexibility of the design which can be easily adjusted by overlapping the curved sheets and adjusting the support structures 18.

The novel revetment design is provided for eliminating bank and cliff erosion on sandy beaches and has a very small width footprint on the beach. The main structure of the design incorporates curved corrugated steel sheets coated with a special sandy colored polyurethane. The curvature of the sheets can be designed as a part of a parabola or a circle. The curved sheets are supported by a superstructure that leans slightly towards the erosion cliff and has a corrugated sheet as the base to link to the structure. The base sheet is held down against the sand by heavy rock such that any lateral forces pushing from the cliff side are counterbalanced by this rock by at least a factor of two. The design has the toe of the curved sheet buried three feet below the sand surface with the tangent at the upper edge of the curvature creating an almost vertical line when the circle equation is used. The design also has pea gravel or drainage rock filling the void behind the curved steel right up to the cliff or bank. The design does not require any armor rock in front of the curved, hence the very short width profile on the beach. It is also possible to attach a railing on the upper edge to provide a safe walkway behind the revetment at a designed elevation depending on the cliff or bank height at the specific location.

Also note that it is important that the toe or bottom edge of the lower sheet near the front rail 17C of the curved sheet is buried at least three (3) feet into the sand with some associated rocks being placed at this level as shown. The base of the structure at the three (3) foot level is comprised of 10 gauge galvanized corrugated steel sheets linked to upward facing support members. These members are connected to and support the curved sheets. The splash apron area as depicted behind the curved sheets is filled with pea gravel or two (2) inch drainage rock fill to allow rain water and water that possibly overflows the top of the curved steel to easily percolate back down the back of the entire structure. This design ensures no water remains behind the structure that could freeze and cause sheet movement in freezing winter weather.

For an average cottage lot frontage of seventy-five (75) feet, the individual curved sheets each cover forty-four (44) linear inches requiring about 21 sheets. They are bolted together to create an impervious continuum. The curved sheets are spray coated with a polyurethane, fire retardant, sandy colored product which creates a very tough, sand paper surface. The thickness of the sprayed product will vary along the sheet being approximately two hundred and forty (240) mils near the bottom to about ninety (90) mils near the top. The reason for this is that there will be more sand/water sediment movement at the bottom of the curve during storm conditions than at the top of the curve leading to increased wear.

This design assumes the waves have “broken” prior to encountering the barrier. As the wave action moves up the curved sheet at 2 to 5 meters per second, its kinetic energy is dissipated as the force of gravity eventually equals the weight of the water and it stops upward movement. It is anticipated that during windy and waving conditions the water movement may not only be upward but may propagate sideways along many sheets. Wind and wave movement from the lake will dictate whether this occurs and in which direction water moves. One of the interesting aspects of this design is its flexibility. By combining two (2) sheets, one overlapping the other, the curved length or generated chord can be varied considerably. This allows the design to be matched to the cliff height and desirability of erosion protection. It is suggested that the minimum height could be set to four (4) feet and the maximum chord length set to about sixteen (16) feet. These values are currently based on the corrugated sheet sizes that are readily available and manufactured in industry.

In the design it is necessary to determine the amount of rock required in the base section to counteract the moment of force caused by the cliff pushing against the upper portion of the structure. A factor of two has been selected as the target and further study will determine the exact rock tonnage required.

The curve of the steel sheets is important in this design. Two types of curves can be implemented although one type would require a manufacturing modification. The curvature can be a section of a circle or can be a section of a parabola. An equation of the form

y=ax ² +bx+c  (1)

represents the generic formula for a parabola. If, for example, an erosion barrier for a fifteen (15) foot high cliff design is required, the following equation has been determined for the parabola with a=0.96, b=−5.81, c=8.80 and x defined in feet. This gives

y=0.96x ²−5.81x+8.80 for 3≦x≦10  (2)

Based on this equation the toe of the parabola would start at about x=3 feet. The advantage of the parabola curve is the rapid, somewhat exponential change in the slope of the curve as it rises almost vertically. A tangent to the curve at the 15 foot level never becomes fully vertical but remains at a very steep slope. This would mean that the kinetic energy of any water mass moving up the curve would soon be balanced by its own weight, stop, fall back on itself or move to the left or right.

The second curve, a circle, has the general equation as follows.

(x−x ₀)²+(y−y ₀)² =r ²  (3)

where x₀ and y₀ are the coordinates of the center of the circle and r represents the radius. As an example, for the design of an erosion barrier curvature based on a circle for a fifteen (15) foot cliff height, the following equation would be used

x ²+(y−15)²=225  (4)

with center at x₀=0 and y₀=15. It creates a more gently inclining curve and has a vertical tangent line occurring only once in the right hand quadrant. Given that the current manufacturing process for curled sheets is based on circles, the current design will focus on equation (3) rather than equation (1). Parabolic designed curves can be implemented in the future by modifying the curling equipment to adjust the amount of curl occurring in real time as the sheet passes through the curling machine. For now, emphasis will be on the circle designed curvature for the erosion barrier.

An important consideration is the length and thickness of the steel sheets that are available from industry for the structure. Steel sheets are roll formed and cut to a maximum length of 116.5±0.3 inches, with a width of 45.5+0.5, −0.3 inches, and a variety of thicknesses ranging from gauge 3 (0.2391″) to gauge 30 (0.0120″). Assuming a fifteen (15) foot high erosion barrier is to be designed based on a curvature given by the circle with equation (4) the length of the arc subtended by 90 degrees as shown in FIG. 1 is calculated as 23.5612 feet. However, only the part of the curve subtended by 70.5 degrees (representing the arc labeled S₁ in FIG. 1 from Toe to the Top edge of the curvature) is required for the design. Essentially, this reduces the footprint of the barrier on the beach by five (5) feet and would require only 18.46 feet of curled steel or 221.56 inches. For the design, two (2) corrugated steel sheets would be required with an overlap of two (2) inches. One sheet would be 116.5 inches in length and the second sheet would be cut to 107.5 inches. A thickness of 0.1046 inch or 12 gauge would be used. The corrugated steel base would be comprised of 88 inch sheets with a suggested thickness of 0.2092 inch or 5 gauge. Support members are anchored to these base sheets.

Sections of the barrier would be fabricated 88 inches wide and then placed in a ready made 3 foot trench at approximately 88 inches apart. On the higher structures as shown here, the curved sections for the upper portion of the barrier are then be installed and secured in place. The lower curved sections would not be installed at this time. Rock is then be placed on the base support corrugations to as high as possible with a bucket no wider than 6.5 feet as it must pass through the support structure. The rock weight should be at least two times the possible lateral forces created by the cliff forces behind the structure pushing towards the lakeshore. Section by section is then added until complete at about 75 feet. During this time sensors for measuring structural integrity can be installed at the back of the upper and mid sections of the curved sheets and support members. Wiring can be installed in EMT to prevent cable damage. Once completed and the necessary rock installed, the lower curved sheets would be installed using self tapping screws at the bottom and nuts and bolts at the mid sections as the structure is gradually fabricated. The area behind the structure would then be filled with pea gravel or drainage rock.

Based on the current cost of the components a maximum price range should be within the $30,000 to $35,000 maximum for a 75 foot frontage giving an installed cost range of $400 to $465 per running foot. Of course, if a number of cottage owners band together then it is presumed that pricing could be better. It is anticipated that the metal component of the structure could be supplied in kits from the manufacturer for a specific locations design height and width requirement.

This design can use curved corrugated steel sheets with a sandy colored polyurethane coat. The only component of this design that will wear would be the polyurethane isomer coating depending on the frequency of storms and the amount of sand carried by the water that would continually move across the lower section of the curved portion of the sheets. This would be examined after every storm that impacts the structure to see how much, if any, of the coating has disappeared.

Ultra-violet sun rays that impact on the coating may cause some signs of fading but is anticipated that the coating should be good for at least 10 to 12 years, after which a new coating might be required. Damaged areas could be re-coated or have a kit supplied to repair small areas. 

1. Apparatus for control of erosion at the shore line of a body of water at an edge of the surface of the body of water comprising: a frame for mounting at the shore line with a base for engaging into the ground and an upper portion for extending upwardly from the ground; at least one curved sheet mounted on and located by the frame; the curved sheet having a lower edge arranged relative to the frame so as to be located at a position below the ground surface; the curved sheet having an upper edge arranged relative to the frame so as to be located at a position above the water surface; the curved sheet having a concave front surface extending from the bottom edge upwardly to the upper surface and curved so that an angle of the surface to horizontal planes increases from the horizontal planes adjacent the bottom edge to horizontal planes adjacent the upper edge.
 2. The apparatus according to claim 1 wherein the curved sheet is substantially vertical at the upper edge.
 3. The apparatus according to claim 1 wherein the frame is formed of a plurality of horizontal rails supporting the curved sheet including a bottom rail at or adjacent the bottom edge and a top rail at or adjacent the top edge.
 4. The apparatus according to claim 1 wherein the rails are connected to upstanding supports which extend from the rails downwardly to the base.
 5. The apparatus according to claim 1 wherein the base includes a receptacle for receiving ballast to hold down the frame in the ground.
 6. The apparatus according to claim 5 wherein the receptacle comprises a base plate onto which ballast in the form of rocks can be loaded.
 7. The apparatus according to claim 6 wherein the base plate is generally planar and generally horizontal.
 8. The apparatus according to claim 1 wherein the curved sheet has the bottom edge thereof spaced from the base.
 9. The apparatus according to claim 1 wherein the at least one curved sheet comprises a plurality of curved panels arranged side by side.
 10. The apparatus according to claim 1 wherein the at least one curved sheet is corrugated with channels which extend longitudinally from the bottom edge to the top edge.
 11. The apparatus according to claim 1 wherein the at least one curved sheet is coated with a sand colored coating at least on the concave front surface.
 12. The apparatus according to claim 1 wherein the base is held down against the sand by heavy rock such that any lateral forces pushing from the cliff side are counterbalanced by this rock by at least a factor of two.
 13. The apparatus according to claim 1 wherein the bottom edge of the curved sheet is buried below the sand surface.
 14. The apparatus according to claim 1 wherein a void behind the curved steel is filled with a drainage material.
 15. The apparatus according to claim 1 wherein there is no armor rock in front of the curved sheet to provide a very short width profile on the beach.
 16. The apparatus according to claim 1 wherein a railing is attached to the frame at or adjacent the upper edge to provide a safe walkway behind the revetment.
 17. The apparatus according to claim 1 wherein the curved sheet has a parabolic or circular curvature. 